Hydraulic pump unit

ABSTRACT

There is provided a hydraulic pump unit of variable displacement type disposed away from a pair of hydraulic motor units which are capable of being independently arranged, the pump unit fluid-connected to the pair of hydraulic motor units so as to change the outputs of the pair of hydraulic motor units in both forward and reverse rotation directions. The pump unit includes a hydraulic pump body operatively rotated and driven by a driving source, a pump case surrounding the hydraulic pump body, a capacity adjusting mechanism for changing the capacity of the hydraulic pump body, and an actuator for operating the capacity adjusting mechanism. The actuator is controlled based on a manual operation signal corresponding to a manual operation amount.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a hydraulic pump unit of variabledisplacement type disposed away from a pair of hydraulic motor unitswhich are capable of being independently arranged, the hydraulic pumpunit fluid-connected to the pair of hydraulic motor units so as tochange the outputs of the pair of hydraulic motor units in both forwardand reverse directions.

2. Related Art

It has been conventionally known that a hydraulic pump unit of variabledisplacement type and a hydraulic motor unit, which are fluid-connectedto each other so as to form an HST, are configured to be capable ofbeing independently arranged.

The hydraulic pump unit and the hydraulic motor unit are particularlyuseful in a working vehicle needing to provide a space between a pair ofdriving wheels so as to stabilize the body posture at the time ofturning such as a mower tractor capable of turning in place (zero turn)(for example, see U.S. Pat. No. 6,425,244).

For details, the hydraulic pump unit of variable displacement type isprovided with a hydraulic pump body operatively rotated and driven by adriving source, and a capacity adjusting mechanism for changing thecapacity of the hydraulic pump body. The output of the hydraulic motorunit can be changed by operating the capacity adjusting mechanism.

However, in the conventional hydraulic pump unit of variabledisplacement type, since the capacity adjusting mechanism is merelyconnected to a manual controlling member such as a traveling levererected from right and left side floors of a driver sheet via amachinery link mechanism, large manual operation power and manualoperation amount are required for the travel operation of a vehicle.

Since the large manual operation power and the manual operation amountare required for the operation of the capacity adjusting mechanism, itis difficult to miniaturize the controlling member.

Furthermore, in the conventional constitution, there is a problem inthat the fluctuation of the load to the hydraulic motor unit causes thefluctuation of the output amount of the hydraulic motor unit even whenthe amount of operation of the manual operation member is constant.

That is, the load to the hydraulic motor unit is fluctuated according totravel conditions such as a state of a travel surface and the existenceof pulling.

When the load fluctuation to the hydraulic motor unit is occurred, theoutput amount of the hydraulic motor unit is fluctuated even when thetilting amount of the capacity adjusting mechanism is constant.

The conventional constitution has not been sufficiently considered inview of this point.

The present invention has been accomplished in view of the prior art,and it is an object of the present invention to provide a hydraulic pumpunit of variable displacement type capable of reducing the manualoperation power and the manual operation amount for changing thecapacity of the hydraulic pump body.

It is another object of the present invention to provide a hydraulicpump unit of variable displacement type capable of obtaining the outputof the hydraulic motor unit corresponding to the amount of operation ofthe manual operation member in spite of the fluctuation of the load tothe hydraulic motor unit forming an HST in cooperation with thehydraulic pump unit.

SUMMARY OF THE INVENTION

According to the present invention, there is provided a hydraulic pumpunit of variable displacement type disposed away from a pair ofhydraulic motor units which are capable of being independently arranged,the pump unit fluid-connected to the pair of hydraulic motor units so asto change the outputs of the pair of hydraulic motor units in bothforward and reverse rotation directions.

The hydraulic pump unit includes a hydraulic pump body operativelyrotated and driven by a driving source, a pump case surrounding thehydraulic pump body, a capacity adjusting mechanism for changing thecapacity of the hydraulic pump body, and an actuator for operating thecapacity adjusting mechanism. The actuator is controlled based on amanual operation signal corresponding to a manual operation amount.

With this configuration, the manual operation power and the manualoperation amount required for operating the capacity adjusting mechanismcan be reduced. Therefore, the manual operation member for operating thecapacity adjusting mechanism can be miniaturized.

Preferably, the actuator is controlled based on a feedback signalcorresponding to outputs of the pair of the hydraulic motor units, inaddition to the manual operation signal.

With this configuration, even when the load fluctuation to the hydraulicmotor units occurs, the output amounts of the hydraulic motor unitscould be corresponded to the operation amount of the travel operationmechanism.

In the above various configurations, the hydraulic pump body maypreferably include first and second hydraulic pump bodies respectivelyand independently fluid-connected to the pair of hydraulic motor units,the capacity adjusting mechanism may include first and second capacityadjusting mechanisms respectively corresponding to the first and secondhydraulic pump bodies, and the actuator may include first and secondactuators respectively corresponding to the first and second capacityadjusting mechanisms.

Alternatively, in a case where the pair of hydraulic motor units arefluid-connected to each other so as to form a closed circuit, thehydraulic pump body may include a single hydraulic pump body fortraveling fluid-connected to the closed circuit, and a hydraulic pumpbody fluid-connected to the other hydraulic actuator other than the pairof hydraulic motor units.

In the above various configurations, the actuator may be a hydraulicservomechanism. The hydraulic servomechanism includes a servo pistonoperatively connected to the capacity adjusting mechanism andaccommodated in a reciprocating manner within a piston accommodatingchamber so as to divide the piston accommodating chamber into a regularrotation oil chamber and a reverse rotation oil chamber, asupply/discharge oil passage for supplying operating oil to anddischarging it from the servo piston, and an electromagnetic valve forswitching the supply/discharge oil passage.

Alternatively, the actuator may be an electronic motor operativelyconnected to the capacity adjusting mechanism.

Preferably, the electronic motor is connected to the capacity adjustingmechanism via a reduction gear mechanism.

BRIEF DESCRIPTION OF THE DRAWINGS

The above, and other objects, features and advantages of the presentinvention will become apparent from the detailed description thereof inconjunction with the accompanying drawings wherein.

FIG. 1 is a schematic side view of a working vehicle to which ahydraulic pump unit according to a first embodiment of the presentinvention is applied.

FIG. 2 is a schematic perspective view of the working vehicle shown inFIG. 1.

FIG. 3 is a hydraulic circuit diagram of the working vehicle shown inFIGS. 1 and 2.

FIG. 4 is a sectional view taken in IV-IV line in FIG. 1.

FIG. 5 is a sectional view taken in V-V line in FIG. 4.

FIG. 6 is a sectional view taken in VI-VI line in FIG. 5.

FIG. 7 is a sectional view taken in line VII-VII in FIG. 6.

FIG. 8 (a) is a schematic control diagram showing a controlling methodof electromagnetic valves in the hydraulic pump unit according to thefirst embodiment.

FIG. 8 (b) is a schematic control diagram showing another controllingmethod of the electromagnetic valves.

FIG. 8 (c) is a schematic control diagram showing a controlling methodof the electromagnetic valves in a case where the hydraulic pump unit ofthe first embodiment is applied to a working vehicle with a singletraveling operation member.

FIG. 8 (d) is a schematic control diagram showing another controllingmethod of the electromagnetic valves in a case where the hydraulic pumpunit of the first embodiment is applied to a working vehicle with asingle traveling operation member.

FIG. 9 is a schematic perspective view of another working vehicle towhich the hydraulic pump unit of the first embodiment is applied.

FIG. 10 is a perspective view of an example of a travel operationmechanism in the working vehicle.

FIG. 11 is a sectional view of a hydraulic pump unit according to asecond embodiment.

FIG. 12 is a sectional view of a hydraulic pump unit according to athird embodiment.

FIG. 13 is a hydraulic circuit diagram of a working vehicle to which ahydraulic pump unit according to a fourth embodiment is applied.

FIG. 14 is an exploded perspective view of the hydraulic pump unit ofthe fourth embodiment.

FIG. 15 is an exploded perspective view of a hydraulic pump unitaccording to a fifth embodiment.

FIG. 16 is a sectional view of a hydraulic pump unit according to asixth embodiment.

FIG. 17 is a hydraulic circuit diagram of a working vehicle to which ahydraulic pump unit according to a seventh embodiment is applied.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1

Hereinafter, a preferred embodiment of a hydraulic pump unit accordingto the present invention will be described referring to the accompanyingdrawings.

FIGS. 1 and 2 show a schematic side view and a schematic perspectiveview of a working vehicle 1 to which a hydraulic pump unit 100Aaccording to the present embodiment is applied, respectively.

FIG. 3 shows a hydraulic circuit diagram of the working vehicle 1.

As shown in FIGS. 1 to 3, the working vehicle 1 is provided with avehicle frame 8, a driving source 2 supported by the vehicle frame 8, apair of right and left driving wheels 3 (rear wheels in the presentembodiment), caster wheels 4 (a pair of front wheels in the presentembodiment), first and second hydraulic motor units 20 a, 20 b forrespectively and independently driving the pair of driving wheels 3, ahydraulic pump unit 100A of variable displacement type according to thepresent embodiment, and a travel operation mechanism 10 for changing thesupply-discharge oil amount of the hydraulic pump unit 100A and capableof being manually operated.

Numeral 15 in FIG. 1 or 2 designates a driver seat. A nearly T-shapedsteering post is erected from a floor in front of the driver seat 15,and the travel operation mechanism 10 is arranged on the upper surfaceof the post. Numeral 7 designates a mower apparatus supported by thevehicle frame 8 so as to be located between the driving wheels 3 and thecaster wheels 4 in the longitudinal direction of the vehicle.

In the working vehicle 1, the mower apparatus 7 is operatively driven bythe driving source 2 via a pulley/belt mechanism.

The first and second hydraulic motor units 20 a, 20 b can beindependently arranged to each other, and are symmetrically arranged ina vehicle width direction so as to be located near the correspondingdriving wheels 3.

The first and second hydraulic motor units 20 a, 20 b respectively havefirst and second motor shafts 21 a, 21 b operatively connected to thecorresponding driving wheels 3, and first and second hydraulic motorbodies 22 a, 21 b for rotating and driving the corresponding motorshafts 21 a, 21 b.

In the present embodiment, both the first and second hydraulic motorunits 20 a, 20 b are of a fixed displacement type in which thesupply-discharge oil amount of the hydraulic motor bodies are fixed.

FIG. 4 shows a longitudinal sectional front view of the hydraulic pumpunit 100A taken in IV-IV line in FIG. 1.

FIGS. 5 and 6 show sectional front views taken in V-V line in FIG. 4 andtaken in VI-VI line in FIG. 5, respectively.

As shown in FIGS. 4 to 6, the hydraulic pump unit 100A is provided witha hydraulic pump body 110 operatively rotated and driven by the powerfrom the driving source 2, a pump case 120 for surrounding the hydraulicpump body, a capacity adjusting mechanism 130 for changing the capacityof the hydraulic pump body, and an actuator 200 for operating thecapacity adjusting mechanism 130 according to a manual operation.

In the present embodiment, the hydraulic pump unit 100A has first andsecond hydraulic pump bodies 110 a, 110 b as the hydraulic pump body110.

The first hydraulic pump body 110 a is fluid-connected to the firsthydraulic motor body 22 a via a pair of first operation oil lines 300 aso as to form a first HST in cooperation with the first hydraulic motorbody 22 a.

The second hydraulic pump body 110 b is fluid-connected to the secondhydraulic motor body 21 b via a pair of second operation oil lines 300 bso as to form a second HST in cooperation with the second hydraulicmotor body 22 a.

The hydraulic pump unit 100A, therefore, has first and second capacityadjusting mechanisms 130 a, 130 b for respectively changing thecapacities of the first and second hydraulic pump bodies 110 a, 110 b asthe capacity adjusting mechanism 130, and has first and second actuators200 a, 200 b for respectively operating the first and second capacityadjusting mechanisms 130 a, 130 b as the actuator 200.

The hydraulic pump unit 100A is further provided with an input shaft 140supported by the pump case 120 so as to be operatively connected to thedriving source 2, first and second pump shafts 150 a, 150 b supported bythe pump case 120 so as to rotate and drive the first and second pumpbodies 110 a, 110 b, respectively, and a power transmission mechanism160 accommodated in the pump case 120 so as to transmit the power fromthe input shaft 140 to the first and second pump shafts 150 a, 150 b.

In the present embodiment, the input shaft 140 and the first pump shaft150 a are integrally formed by a single shaft 145 (see FIGS. 4, 5).

The pump case 120 is configured so as to accommodate both the first andsecond hydraulic pump bodies 110 a, 110 b.

Specifically, the pump case 120 has a single case body 170, a singleport block 180 (center section) detachably connected to the case body170, and a single lid member 190 detachably connected to the case body170.

As shown in FIGS. 4 to 6, the case body 170 has an end wall 171extending in the direction substantially orthogonal to the axis linedirection of the pump shafts 150 a, 150 b, and a peripheral wall 172extending in the axis line direction of the pump shaft 150 a, 150 b fromthe peripheral portion of the end wall 171.

The peripheral wall 172 has an opening at a free end side opposite tothe end wall 171.

The opening is set to a size enough to insert the first and secondhydraulic pump bodies 110 a, 110 b theretrough.

The port block 180 has supply/discharge oil passages for the first andsecond hydraulic pump bodies 110 a, 110 b. The port block 180 isconnected to the case body 170 so as to liquid-tightly close the openingin a state where the supply/discharge oil passages are fluid-connectedto the first and second hydraulic pump bodies 110 a, 110 b.

That is, the first and second hydraulic pump bodies 110 a, 110 b areaccommodated in a pump accommodating space defined by the case body 170and the port block 180.

The lid member 190 is connected to the case body 170 so as to define apower transmission mechanism accommodating space for accommodating thepower transmission mechanism 160 between the lid member 190 and the endwall 171.

The input shaft 140 is supported by the pump case 120 with a first endforming an input end extended outward.

As shown in FIG. 1, the driving source 2 is of a vertical crankshafttype in the present embodiment. Therefore, the input shaft 140 issupported by the pump case 120 so that the input end is projectedvertically. However, when the driving source 2 is of a horizontalcrankshaft type, the input shaft may be supported by the pump case 120so that the input end is horizontally projected.

The first and second pump shafts 150 a, 150 b are supported at the bothsides by the lid member 190 and the plate member 180 so as to supportthe corresponding hydraulic pump bodies 110 a, 110 b within the pumpaccommodating space.

At least one end of one of or both the first and second pump shafts 150a, 150 b is preferably projected outward from the pump case 120.

The projecting end is used as a driving shaft for a charge pump bodyand/or other rotating member attached to the hydraulic pump unit 100A ifdesired.

In the present embodiment, as described above, the input shaft 140 andthe first pump shaft 150 a are integrally formed by the single shaft145.

As shown in FIG. 4, the single shaft 145 has a first end projectingoutward through the lid member 190 so as to form the input end and asecond end projecting outward through the port block 180.

The second end of the single shaft 145 acts as a driving shaft for acharge pump body 410 to be described later.

In the present embodiment, the first end of the single shaft 145 formsthe input end operatively connected to the driving source 2, and alsoacts as a driving shaft for a cooling fan 450 (see FIG. 3).

In the present embodiment, as shown in FIG. 4, the second pump shaft 150b has a second end projecting outward through the port block 180 so asto output the rotation power to the exterior.

The power transmission mechanism 160 is configured so as to transmit thepower from the input shaft 140 to the first and second pump shafts 150a, 150 b.

In the present embodiment, as shown in FIGS. 4, 5, the powertransmission mechanism 160 has a driving gear 161 supported in arelatively non-rotatable manner on the single shaft 145, and a drivengear 162 supported in a relatively non-rotatable manner on the secondpump shaft 150 b so as to be engaged with the driving gear 161.

As shown in FIGS. 4, 5, the first and second hydraulic pump bodies 110a, 110 b include cylinder blocks 111 supported in a relativelynon-rotatable manner on the corresponding pump shafts 150 a, 150 bwithin the pump accommodating space, and piston units 112 accommodatedin the corresponding cylinder blocks 111 in a reciprocating manner alongthe axis line direction and in a relatively non-rotatable manner.

The first and second capacity adjusting mechanisms 130 a, 130 b includeoutput adjusting members 131 for changing the reciprocating range of thepiston unit 112 in the corresponding hydraulic pump bodies 110 a, 110 baccording to its tilting position, and control shafts 132 having a baseend operatively connected to the corresponding output adjusting member131 so as to tile the corresponding output adjusting member 131.

As shown in FIG. 4, in the present embodiment, a cradle type movableswash plate is used as the output adjusting member 131.

That is, a recessed arching swash plate receiving surface 175 is formedon the inner surface (the surface facing the hydraulic pump bodies 110a, 110 b) of the end wall 171. The cradle type movable swash plate 131is configured so that one end surface is operatively engaged with thefree end of the piston unit 112 and the other end surface is engagedwith the arching swash plate receiving surface 175 via a thrust metalhaving the same shape.

The control shaft 132 is supported by the peripheral wall 172 of thecase body 170 in a rotatable manner about its axis, and is configured totile the movable swash plate 131 by rotating about its axis.

For details, as shown in FIGS. 5, 6, the control shaft 132 is supportedin a rotatable manner about its axis by the peripheral wall 172 of thecase body 170 in a state where the base end is operatively connected tothe movable swash plate 131 via an arm 133 and the tip end can beaccessed from outside of the pump case 120.

FIG. 7 shows a sectional view of the first and second actuators 200 a,200 b taken in line VII-VII in FIG. 6.

As shown in FIGS. 3 and 5 to 7, the hydraulic pump unit 100A includesfirst and second hydraulic servomechanisms 201 a, 201 b as the first andsecond actuators 200 a, 200 b.

The first and second hydraulic servomechanisms 201 a, 201 b respectivelyhave servo pistons 210 a, 210 b reciprocatingly accommodated in thepiston accommodating chambers in a state where the servo pistons 210 a,210 b are operatively connected to the corresponding capacity adjustingmechanisms 130 a, 130 b, a servo supply/discharge oil passage forsupplying operating oil to and discharging it from the servo pistons 210a, 210 b, and electromagnetic valves 220 a, 220 b for switching theservo supply/discharge oil passage.

In the present embodiment, the piston accommodating chambers are definedby servo piston cases 230 a, 203 b removably connected to the pump case120, and the electromagnetic valves 220 a, 220 b are mounted in portplates 280 a, 280 b connected to the corresponding servo piston cases230 a, 230 b.

Specifically, as shown in FIGS. 5 to 7, the first hydraulicservomechanism 201 a is provided with a first servo piston case 230 aremovably connected to the pump case 120, a first servo piston 210 aaccommodated in a first piston accommodating chamber defined by thefirst servo piston case 230 a, a first servo supply/discharge oilpassage for supplying operating oil to and discharging it from the firstservo piston 210 a, and an electromagnetic valve for a first regularrotation oil chamber 220 a(F) and an electromagnetic valve for a firstreverse rotation oil chamber 220 a(R), the electromagnetic valves beingconfigured to switch the first servo supply/discharge oil passage.

The second hydraulic servomechanism 201 b has substantially the sameconstitution as that of the first hydraulic servomechanism 201 a.

The corresponding members in the figures are, therefore, designated bythe same numerals or the same numerals with replacing subscripts with b,and the detailed description thereof are omitted.

The first servo piston 210 a is reciprocatingly accommodated in thefirst piston accommodating chamber so as to define a first regularrotation oil chamber 231 a (F) and a first reverse rotation oil chamber231 a (R).

That is, the first piston accommodating chamber has the first regularrotation oil chamber 231 a (F) and the first reverse rotation oilchamber 231 a (R) respectively provided at one side and the other sideof the axis line direction of the servo piston 210 a so as to sandwichthe first servo piston 210 a.

The first servo piston 210 a is operatively connected to the tip end ofthe corresponding control shaft 132 in a state where the first servopiston 210 a is accommodated in the first piston accommodating chamberin a reciprocating manner.

In the present embodiment, as shown in FIGS. 6 and 7, the first servopiston 210 a is operatively connected to the tip end of the controlshaft 132 via a first crank arm 240 a.

The first servo piston case 230 a is configured so that the axis linedirection of the first servo piston 210 a is parallel to the pump shaft150 a.

Alternatively, the first servo piston case 230 a may be configured sothat the axis line direction of the first servo piston 210 a isperpendicular to the pump shaft 150 a.

The first crank arm 240 a has a base end portion connected to thecorresponding control shaft 132 in a relatively non-rotatable manneraround the axis of the control shaft 132, an arm portion extendingoutward in the radial direction from the base end portion on the basisof the axis line of the corresponding control shaft 132, and an engagingportion extending in the axis line direction of the correspondingcontrol shaft 132 from the free end side of the arm portion.

The engaging portion of the first crank arm 240 a is engaged with theouter peripheral surface of the first servo piston 210 a via an accessopening 231 formed on the first servo piston case 230 a.

For details, an engaging groove 211 is formed in the directionorthogonal to the axis line of the first servo piston 210 a on the outerperipheral surface of the first servo piston 210 a, and the engagingportion of the first crank arm 240 a is engaged into the engaging groove211.

According to the constitution, when the first servo piston 210 a ispushed toward the regular rotation direction of one side of the axisline direction, the engaging portion of the first crank arm 240 aengaged into the engaging groove 211 is oscillated to one side aroundthe corresponding control shaft 132, and thereby the control shaft 132is rotated to the regular rotation direction around the axis line.

Similarly, when the first servo piston 210 a is pushed toward thereverse rotation direction of the other side of the axis line direction,the engaging portion of the first crank arm 240 a engaged into theengaging groove 211 is oscillated to the other side around thecorresponding control shaft 132, and thereby the control shaft 132 isrotated to the reverse rotation direction around the axis line.

In the figures, numeral 245 designates a roller externally inserted ontothe engaging portion of the first crank arm 240 a, and numeral 215designates a pair of neutral returning springs for keeping the firstservo piston 210 a at a neutral position when oil pressure is notapplied to the first servo piston 210 a.

As shown in FIGS. 3, 5 and 7, the supply/discharge oil passage has afirst servo input passage 351 a having a first end fluid-connected to ahydraulic pressure source (a charge pump body 410, which is describedlater, in the present invention), a first regular rotation passage 352 ahaving a first end fluid-connected to the first regular rotation oilchamber 231 a(F), a first reverse rotation passage 353 a having a firstend fluid-connected to the first reverse rotation oil chamber 231 a (R),and a first servo drain passage 354 a having a first end fluid-connectedto an oil tank (the internal space of the pump case 120 in the presentinvention).

The first regular rotation oil chamber side electromagnetic valve 220 a(F) is configured so as to selectively take a neutral position where thefirst regular rotation passage 352 a is blocked, a regular rotationposition where the first servo input passage 351 a is fluid-connected tothe first regular rotation passage 352 a, and a reverse rotationposition where the first servo drain passage 354 a is fluid-connected tothe first regular rotation passage 352 a, according to a control signalto be described later.

Similarly, the first reverse rotation oil chamber side electromagneticvalve 220 a (R) is also configured so as to selectively take a neutralposition where the first reverse rotation passage 353 a is blocked, aregular rotation position where the first servo drain passage 354 a isfluid-connected to the first reverse rotation passage 353 a, and areverse rotation position where the first servo input passage 351 a isfluid-connected to the first reverse rotation passage 353 a, accordingto a control signal to be described later.

With the construction, when both the first regular rotation oil chamberside electromagnetic valve 220 a (F) and the first reverse rotation oilchamber side electromagnetic valve 220 a (R) are positioned at “theneutral position”, “the regular rotation position” and “the reverserotation position”, the first servo piston 210 a is held at the neutralposition, moved to the regular rotational direction, and moved to thereverse rotational direction, respectively.

In the present embodiment, the first and second hydraulicservomechanisms 201 a and 201 b also have manual operation mechanisms290 for manually operating the corresponding capacity adjustingmechanisms 130 a and 130 b.

The manual operation mechanism 290 is provided for tilting thecorresponding capacity adjusting mechanisms 130 a and 130 b by themanual operation when the operation oil cannot be supplied to the firstand second hydraulic servomechanisms 201 a and 201 b by some reasons.

Specifically, as shown in FIGS. 5 to 7, the manual operation mechanism290 is provided with a manual operation shaft 291 supported in arotatable manner around its axis, a connecting member 292 having a baseend connected to the manual operation shaft 291 in a relativelynon-rotatable manner and a free end operatively connected to thecorresponding servo pistons 210 a and 210 b, and a manual operation arm293 having a base end connected to the manual operation shaft in arelatively non-rotatable manner. The manual operation mechanism 290 isconfigured so that the corresponding capacity adjusting mechanisms 130 aand 130 b can be tilted via the corresponding servo pistons 210 a and210 b by oscillating the manual operation arm 293 around the manualoperation shaft 291.

In addition to the constitution, the hydraulic pump unit 100A may beprovided with at least a charge pump unit 400 rotated and driven by thefirst or second pump shafts 150 a, 150 b.

In the present embodiment, as shown in FIGS. 4, 5, the hydraulic pumpunit 100A is provided with a single charge pump body 410 rotated anddriven by the first pump shaft 150 a, and a charge pump case 420connected to the port block 180 so as to surround the charge pump body410.

Herein, a hydraulic circuit in the working vehicle 1 according to thepresent embodiment will be described.

As shown in FIG. 3, the working vehicle 1 is provided with the pair offirst operation oil lines 300 a for fluid-connecting the first hydraulicpump body 110 a and the first hydraulic motor body 22 a, the pair ofsecond operation oil lines 300 b for fluid-connecting the secondhydraulic pump body 110 b and the second hydraulic motor body 22 b, asuction line 310 having a first end fluid-connected to an oil tank 16and a second end fluid-connected to the suction side of the charge pumpbody 410, a discharge line 320 having a first end fluid-connected to thedischarge side of the charge pump body 410, a charge line 330 having afirst end fluid-connected to the discharge line 320 and second endsfluid-connected to the pair of first operation oil lines 300 a and thepair of second operation oil lines 300 b via check valves 335,respectively, a servo input line 340 having a first end fluid-connectedto the discharge line 320 and second ends fluid-connected to the firstand second hydraulic servomechanisms 201 a, 210 b, a first servo drainline 360 a having a first end fluid-connected to the first hydraulicservomechanism 201 a and a second end fluid-connected to an oilreservoir (in the present embodiment, the interior space of the pumpcase 120), and a second servo drain line 360 b having a first endfluid-connected to the second hydraulic servomechanism 201 b and asecond end fluid-connected to the oil reservoir (in the presentembodiment, the interior space of the pump case 120).

The pair of first operation oil lines 300 a includes a pair of firstoperation passages 301 a formed in the port block 180 so as to havefirst ends respectively fluid-connected via a pair of kidney ports tothe first hydraulic pump body 110 a and second ends opened to the outersurface to form a pair of first operation oil ports 301 a (P), and apair of first conduits 302 a extending between the pair first operationoil ports 301 a (P) and the first hydraulic motor unit 20 a.

The pair of first operation oil lines 300 b includes a pair of secondoperation passages 301 b formed in the port block 180 so as to havefirst ends respectively fluid-connected via a pair of kidney ports tothe second hydraulic pump body 110 b and second ends opened to the outersurface to form a pair of second operation oil ports 301 b (P), and apair of second conduits 301 b extending between the pair secondoperation oil ports 301 b (P) and the second hydraulic motor unit 20 b.

The suction line 310 includes a suction conduit 311 which has a firstend fluid-connected to the oil tank 16 and in which a filter 315 isinterposed, and a suction passage 312 formed in the charge pump case420.

The suction passage 312 has a first end forming a suction port 312 (P)to which the suction conduit 311 is connected and a second endfluid-connected to the suction side of the charge pump body 410.

The discharge line 320 has a discharge passage 321 (see FIG. 5) formedin the charge pump case 420 so as to have a first end fluid-connected tothe discharge side of the charge pump body 410.

The discharge passage 321 has a discharge port 322 (P) for charge openedto an abutting surface with the port block 180 and a discharge port 323(P) for servo opened to the outer surface.

The charge line 330 has a charge passage 331 formed in the port block180 so as to have a first end forming a charge port 331 (P)fluid-connected to the discharge port 322 (P) for charge and second endsrespectively fluid-connected to the pair of first operation passages 301a and the pair of second operation passages 301 b via the check valves335.

The servo input line 340 has a first servo conduit 341 a having a firstend fluid-connected to the servo discharge port 323 (P) and a second endfluid-connected to the first servo input passage 351 a, the first servoinput passage 351 a, a second servo conduit 341 b having a first endfluid-connected to the servo discharge port 323 (P) and a second endfluid-connected to a second servo input passage 351 b, and the secondservo input passage 351 b.

The first servo drain line 360 a has the first servo drain passage 354 aformed in the first port plate 280 a, the first servo piston case 230 aand the pump case 120.

Similarly, the second servo drain line 360 b has the second servo drainpassage 354 b formed in the second port plate 280 b, the second servopiston case 230 b and the pump case 120.

As shown in FIG. 3, the working vehicle 1 according to the presentembodiment further includes a first bypass line 370 a which communicatesbetween the pair of first operation oil lines 300 a and in which abypass valve 375 for communicating/blockading the first bypass line 370a is interposed, a second bypass line 370 b which communicates betweenthe pair of second operation oil lines 300 b and in which a bypass valve375 for communicating/blockading the second bypass line 370 b isinterposed, a self-suction line 380 for self-sucking oil from the oilreservoir (the interior space of the housing 120) to either one of thepair of first operation oil lines 300 a or either one of the pair ofsecond operation oil lines 300 b having become the negative pressure atthe time of stopping the charge pump body 410, and a hydraulic pressuresetting line 390 for setting the hydraulic pressure of the dischargeline 320.

In the self-priming line 380, a check valve 385 is interposed so as toallow the oil to flow from the oil reservoir to the negative pressureline of the pair of first operation oil lines 300 a or the negativepressure line of the pair of second operation oil lines 300 b andprevent the reverse flow.

A relief valve 395 is interposed in the hydraulic pressure setting line390.

Herein, the control method of the first regular rotation oil chamberside electromagnetic valve 220 a(F) and the first reverse rotation oilchamber side electromagnetic valve 220 a(R), and the second regularrotation oil chamber side electromagnetic valve 220 b(F) and the secondreverse rotation oil chamber side electromagnetic valve 220 b(R) will beexplained.

Each of the electromagnetic valves 220 a and 220 b is operativelycontrolled by the manual operation signal based on the amount ofoperation of the travel operation mechanism 10.

As shown in FIG. 2, in the present embodiment, the working vehicle 1 isprovided with a first and second operation members 50L and 50R forindependently operating the first capacity adjusting mechanism 130 a andthe second capacity adjusting mechanism 130 b respectively, as thetravel operation mechanism 10.

The first regular rotation oil chamber side electromagnetic valve 220 a(F) and the first reverse rotation oil chamber side electromagneticvalve 220 a (R) are operatively controlled based on the manual operationsignal corresponding to the operation amount including the operationdirection of the first operation member 50L. The second regular rotationoil chamber side electromagnetic valve 220 b (F) and the second reverserotation oil chamber side electromagnetic valve 220 b (R) areoperatively controlled based on the manual operation signalcorresponding to the amount of operation including the operationdirection of the second operation member 50R.

Numeral 12 shown in FIG. 2 designates a meter panel for displaying thetravel speed of the vehicle and the vehicle posture relating to thepitching or rolling when traveling on a sloping ground.

FIG. 8 (a) shows a schematic control diagram of the electromagneticvalves 220 a and 220 b in the working vehicle 1.

Specifically, as shown in FIG. 8 (a), the working vehicle 1 is providedwith a control part 30, a first manual operation amount sensor 40 a fordetecting the manual operation amount of the first operation member 50L,and a second manual operation amount sensor 40 b for detecting themanual operation amount of the second operation member 50R. The controlpart 30 outputs the manual operation signal corresponding to thedetecting signal from the first and second manual operation amountsensors 40 a and 40 b to the electromagnetic valves 220 a and 220 b.

As described above, the hydraulic pump unit 100A according to thepresent embodiment is configured so as to operate the first and secondcapacity adjusting mechanisms 130 a and 130 b by utilizing the first andsecond actuators 200 a, 200 b (the first and second hydraulicservomechanism 201 a, 201 b).

Therefore, the manual operation power and the manual operation amountfor operating the first and second capacity adjusting mechanisms 130 a,130 b can be reduced.

In the present embodiment, the working vehicle 1 uses the first andsecond operation members 50L, 50R that are independent to each other andare arranged on the steering post in front of the driver seat as thetravel operation mechanism 10. Alternatively, a single operation member50 (See FIG. 9) arranged on the steering post may be used as the traveloperation mechanism 10.

FIG. 10(a) shows the perspective view of the single operation member 50.

The operation member 50 is so configured to be oscillated around both atraveling referential shaft 500 and a steering referential shaft 510,which are orthogonal to each other, based on the operation of a singleoperation portion 51.

In the modified embodiment provided with the operation member 50, theelectromagnetic valves 220 a and 220 b are operatively controlled basedon the amount of operation (including the operation direction) aroundthe travel referential shaft 500 and the amount of operation (includingthe operation direction) around the steering referential shaft 510.

Specifically, the operation member 50 is provided with a bifurcated bodymember 60 having a pair of bearing portions 61, a grip member 70connected to the body member 60 and forming the operation portion 51,and a cruciform joint member 80 connected to the body member 60 in arelatively rotatable manner via the travel referential shaft 500.

The cruciform joint member 80 has a forward/reverse shaft portion 81supported in a rotatable manner around its axis by the pair of bearingportions 61 via the traveling referential shaft 500, and a steeringshaft portion 82 extending in a direction orthogonal to theforward/reverse shaft portion 81.

As described above, the forward/reverse shaft portion 81 is supported ina rotatable manner around its axis by the body member 60 via thetraveling referential shaft 500.

The steering shaft portion 82 has a bearing hole formed therein, and issupported in a rotatable manner around its axis by the steeringreferential shaft 510 provided on the vehicle frame via the bearinghole.

In the modified embodiment provided with the operation member 50, asshown in FIGS. 8(c) and 10, a speed amount detecting sensor 41 a fordetecting the amount of operation around the travel referential shaft500 and a steering amount detecting sensor 41 b for detecting the amountof operation around the steering referential shaft 510 are providedinstead of the first manual operation amount sensor 40 a and the secondmanual operation amount sensor 40 b.

The control part 30 operatively controls the electromagnetic valves 220a and 220 b so that the first and second capacity adjusting mechanisms130 a and 130 b are tilted in the same direction by the amountcorresponding to the detecting signal of the speed amount detectingsensor 41 a, and operatively controls the electromagnetic valves 220 aand 220 b so that the first and second capacity adjusting mechanisms 130a and 130 b are tilted in the opposite direction by the amountcorresponding to the detecting signal of the steering amount detectingsensor 41 b.

More specifically, when the control part 30 detects the oscillation ofthe operation member 50 to one side (XI direction in FIG. 10) around thetravel referential shaft 500 based on the detecting signal from thespeed amount detecting sensor 41 a, the control part 30 operativelycontrols the electromagnetic valves 220 a and 220 b so that both thefirst and second capacity adjusting mechanisms 130 a and 130 b aretilted in the forward direction by the same amount corresponding to thedetecting signal.

Similarly, when the control part 30 detects the oscillation of theoperation member 50 to the other side (X2 direction in FIG. 10) aroundthe travel referential shaft 500 based on the detecting signal from thespeed amount detecting sensor 41 a, the control part 30 operativelycontrols the electromagnetic valves 220 a and 220 b so that both thefirst and second capacity adjusting mechanisms 130 a and 130 b aretilted in the reverse direction by the same amount corresponding to thedetecting signal.

By contrast, when the control part 30 detects the oscillation of theoperation member 50 to one side (Y1 direction in FIG. 10) around thesteering referential shaft 510 based on the detecting signal from thesteering amount detecting sensor 41 b, the control part 30 operativelycontrols the electromagnetic valves 220 a and 220 b so that the firstcapacity adjusting mechanism 130 a is tilted in the forward directionand the second capacity adjusting mechanism 130 b is tilted in thereverse direction by the amount corresponding to the detecting signal.

Similarly, when the control part 30 detects the oscillation of theoperation member 50 to the other side (Y2 direction in FIG. 10) aroundthe steering referential shaft 510 based on the detecting signal fromthe steering amount detecting sensor 41 b, the control part 30operatively controls the electromagnetic valves 220 a and 220 b so thatthe first capacity adjusting mechanism 130 a is tilted in the reversedirection and the second capacity adjusting mechanism 130 b is tilted inthe forward direction by the amount corresponding to the detectingsignal.

That is, the operation member 50 can be operated within an operableregion defined by a first zero turn position TRmax where the operationmember 50 is maximumly oscillated to one side about the steeringreferential shaft 510 at the neutral position around the travelingreferential shaft 500, a second zero turn position TLmax where theoperation member 50 is maximumly oscillated to the other side around thesteering referential shaft 510 at the neutral position around thetraveling referential shaft 500, a forward maximum output position Fmaxwhere the operation member 50 is maximumly oscillated to one side aroundthe traveling referential shaft 500 at the neutral position around thesteering referential shaft 510, and a reverse maximum output positionRmax where the operation member 50 is maximumly oscillated to the otherside around the traveling referential shaft 500 at the neutral positionof the steering referential shaft 510.

When the current operation position within the operable region of theoperation member 50 is detected by the speed amount detecting sensor 41a and the steering amount sensor 41 b, the control part 30 sends theoutput signal corresponding to the detecting signal to theelectromagnetic valves 220 a and 220 b.

In the vehicle provided with the single operation member 50, the drivergrips the operation member 50 only by one hand with the other hand beingfree. Thereby, the posture of the driver at the time of operation ishardly stabilized.

In view of this point, the handrail 11 may be preferably provided on thesteering post in front of the driver seat 15, as shown in FIG. 9.

As shown in FIGS. 8(b) and 8(d), the electromagnetic valves 220 a and220 b may be preferably controlled based on feedback signalscorresponding to the output amounts of the first and second hydraulicmotor units 20 a and 20 b in addition to the manual operation signal.

Specifically, the working vehicle 1 may be provided with first andsecond output sensors 42 a and 41 b for respectively detecting therotational amounts (including the rotational direction) of the first andsecond motor shafts 21 a and 21 b.

The electromagnetic valves 220 a and 220 b may be operatively controlledby the feedback signal from the first and second output sensors 42 a and42 b, in addition to the manual operation signal based on the first andsecond manual operation amount sensors 40 a and 40 b or the manualoperation signal based on the speed amount detecting sensor 41 a and thesteering amount detecting sensor 41 b.

With the thus constructed feedback circuit, the relationship between theamount of operation of the travel operation mechanism 10 and the outputamounts of the hydraulic motor units 20 a and 20 b can be maintained tobe constant in spite of the load fluctuation to the hydraulic motorunits 20 a and 20 b.

Specifically, the load to the first and second hydraulic motor units 20a and 20 b is fluctuated according to travel conditions such as a stateof a travel surface and the existence of pulling.

That is, even when the amount of operation of the travel operationmechanism 10 is constant, for example, the actual travel speed of theworking vehicle 1 in a state of traveling on an upward inclined groundis different from that of the working vehicle 1 in a state of travelingon a downward inclined ground.

By contrast, the provision of the feedback circuit allows the outputamounts of the first and second hydraulic motor units 20 a and 20 b tofollow the amount of operation of the travel operation mechanism 10.

In the present embodiment, as described above, the first and secondhydraulic servomechanisms 200 a, 200 b have the servo piston cases(first and second servo piston cases 230 a, 230 b) for exclusive use,respectively. However, instead of the servo piston cases, the first andsecond hydraulic servomechanisms 200 a, 200 b can be provided with asingle servo piston case 230.

Embodiment 2

Hereinafter, another embodiment of the hydraulic pump unit according tothe present invention will be described referring to the accompanyingdrawings.

FIG. 11 shows a sectional view taken in a line orthogonal to pump shaftsof a hydraulic pump unit 100B according to the present embodiment.

As shown in FIG. 11, the hydraulic pump unit 100B according to thepresent embodiment is different from the hydraulic pump unit 100A mainlyin that the piston accommodating chamber is provided in a wall portionof a pump case.

Therefore, the same members as the embodiment 1 in the figures aredesignated by the same numerals, and the detailed description thereofare omitted.

Specifically, the hydraulic pump unit 100B according to the presentembodiment has a case body 170B instead of the case body 170 in thehydraulic pump unit 100A.

As shown in FIG. 11, the case body 170B is constituted so that theperipheral wall defines the first and second piston accommodatingchambers.

In the present embodiment, the first and second piston accommodatingchambers are defined so that the axis line directions of the first andsecond servo pistons 210 a, 210 b are orthogonal to the pump shafts 150a, 150 b. Therefore, so as to prevent the interference of the first andsecond piston accommodating chambers, the first and second pistonaccommodating chambers are positioned so as to face each other acrossthe first and second hydraulic pump bodies 110 a, 110 b.

In the configuration where the axis line direction of the servo pistonis orthogonal to the first and second pump shafts 150 a, 150 b, thefirst and second control shafts may be directly engaged with the firstand second servo pistons, respectively.

According to the hydraulic pump unit 100B, the same effect as that ofthe embodiment 1 can be obtained.

Embodiment 3

Hereinafter, still another embodiment of the hydraulic pump unitaccording to the present invention will be described referring to theaccompanying drawings.

FIG. 12 shows a longitudinal sectional view taken in a line along pumpshafts of the hydraulic pump unit 100C according to the presentembodiment.

The same members as those of the embodiment 1 or 2 are designated by thesame numerals, and the detailed description thereof are omitted.

As shown in FIG. 12, the hydraulic pump unit 100C according to thepresent embodiment is provided with pump cases which respectivelycorrespond to the first and second hydraulic pump bodies 110 a, 110 b.

That is, the hydraulic pump unit 100C is provided with a pair of pumpcases 120C for respectively accommodating the first hydraulic pump body110 a and the second hydraulic pump body 110 b. The pair of pump cases120C are arranged in parallel.

The hydraulic pump unit 100C may be provided with a pair of pulleys 161Crespectively supported by the first and second pump shafts 150 a, 150 b,and a belt 162C wound between the pulleys 161C to which tension isapplied, as the power transmission mechanism 160.

As shown in FIG. 12, the hydraulic pump unit 100C according to thepresent embodiment has a pair of charge pump units 400C respectivelydriven by the first pump shaft 150 a and the second pump shaft 150 b.The pair of charge pump units 400C respectively supply the operation oilto the first and second hydraulic servomechanisms 200 a, 200 b.Alternatively, as in the embodiments 1 and 2, only the single chargepump unit 400C may be provided in the hydraulic pump unit 100C. In thealternative configuration, the operation oil is supplied to the both thefirst and second hydraulic servomechanisms 200 a, 200 b from the singlecharge pump unit 400C.

Though the piston accommodating chamber is defined by the servo pistoncase which is a separate body from the pump case 120C as shown in FIG.12 in the present embodiment, it is possible that the pistonaccommodating chamber is formed by the peripheral wall of thecorresponding pump case 120C instead of the servo piston case, as in thesecond embodiment.

Embodiment 4

Hereinafter, still another embodiment of the hydraulic pump unitaccording to the present invention will be described referring to theaccompanying drawings.

FIG. 13 shows a hydraulic circuit diagram of a working vehicle ID towhich a hydraulic pump unit 100D according to the present embodiment isapplied.

FIG. 14 shows an exploded perspective view of the hydraulic pump unit100D.

The same members as those of the embodiments 1 to 3 are designated bythe same numerals, and the detailed description thereof are omitted.

As shown in FIGS. 13 and 14, the hydraulic pump unit 100D according tothe present embodiment is provided with the first and second electricmotors (first and second servomotors) 202 a and 201 b instead of thefirst and second hydraulic servomechanisms 201 a and 201 b, as the firstand second actuators 200 a and 200 b.

That is, the hydraulic pump unit 100D is configured so that the controlpart 30 operatively controls the first and second electric motors 202 aand 201 b based on the manual operation signal corresponding to themanual operation amount of the travel operation mechanism 10, or themanual operation signal and the feedback signal.

In the present embodiment, the first and second electric motors 202 aand 201 b are configured so that each output shafts 204 is coaxiallywith the corresponding control shaft 132 and is connected in arelatively non-rotatable manner around the axis to the correspondingcontrol shaft 132.

Specifically, each of the first and second electric motors 202 a and 201b has a motor case 203 in which a motor body is accommodated, and anoutput shaft 204 projected from the motor case 203.

The motor case 203 is connected to the pump case 120 via a spacer 205 inwhich a through-hole allowing the connection of the output shaft 204 andthe control shaft 132 is formed.

The output shaft 204 is connected to the corresponding control shaft 132via a coupling 206 in a relatively non-rotatable manner within thethrough-hole.

Although the spacer 205 is a separate body from the electric motor 202and the pump case 120 in the present invention, it is of course that thespacer 205 can be also integrally formed with the electric motor 202 orthe pump case 120.

Embodiment 5

Hereinafter, still another embodiment of the hydraulic pump unitaccording to the present invention will be described referring to theaccompanying drawings.

FIG. 15 shows an exploded perspective view of a hydraulic pump unit 100Eaccording to the present embodiment.

The same members as those of the embodiments 1 to 4 are designated bythe same numerals, and the detailed description thereof are omitted.

The hydraulic pump unit 100E according to the present invention isdifferent from the hydraulic pump unit 100D according to the embodiment4 in that the first and second electric motors 202 a and 201 b areconnected to the corresponding control shafts 132 via link mechanisms270.

In the hydraulic pump unit 100E, the first and second electric motors202 a and 201 b are connected to the control shaft 132 via the linkmechanisms 270, and thereby the capacities of the first and secondelectric motors 202 a and 201 b can be reduced.

In the present embodiment, the link mechanism 270 is provided with acontrol arm 271 connected to the control shaft 132 in a relativelynon-rotatable manner, a motor side arm 272 connected to the output shaft204 in a relatively non-rotatable manner, and a link member 273 forconnecting the control arm 271 and the motor side arm 272.

In the present embodiment, as shown in FIG. 15, the first and secondelectric motors 202 a and 201 b are connected to the pump case 120 via amounting frame 207. However, the first and second electric motors 202 aand 201 b can be connected to the vehicle frame 8 via a proper mountingframe instead of this configuration.

Embodiment 6

Hereinafter, still another embodiment of the hydraulic pump unitaccording to the present invention will be described referring to theaccompanying drawings.

FIG. 16 shows a sectional view of a hydraulic pump unit 100F accordingto the present embodiment.

The same members as those of the embodiments 1 to 5 are designated bythe same numerals, and the detailed description thereof are omitted.

The hydraulic pump unit 100F according to the present embodiment isdifferent from the hydraulic pump unit 100D according to the embodiment4 in that the first and second electric motors 202 a and 201 b areconnected to the corresponding control shafts 132 via reduction gearmechanisms 275.

In the hydraulic pump unit 100F, the first and second electric motors202 a and 201 b are connected to the control shaft 132 via the reductiongear mechanisms 275, and thereby the capacities of the first and secondelectric motors 202 a and 201 b can be reduced.

In the present embodiment, the reduction gear mechanism 275 is providedwith a worm gear 276 operatively connected to the output shaft 204, andan arm member 277 which connected to the control shaft 132 and in whicha gear engaged with the worm gear 276 is arranged in circular arc shape.With this configuration, the reduction gear mechanisms 275 can be madecompact, while obtaining a predetermined reduction ratio.

The numeral 208 in FIG. 16 designates a mounting frame for supportingthe motor case 203 of the electric motors 202 a and 202 b, and the wormgear 276 is supported by the mounting frame 208.

Embodiment 7

Hereinafter, still another embodiment of the hydraulic pump unitaccording to the present invention will be described referring to theaccompanying drawings.

FIG. 17 shows a hydraulic circuit diagram of a working vehicle 1G towhich a hydraulic pump unit 100G according to the present embodiment isapplied.

The same members as those of the embodiments 1 to 6 are designated bythe same numerals, and the detailed description thereof are omitted.

As shown in FIG. 17, the hydraulic pump unit 100G according to thepresent embodiment is configured so as to use the first hydraulic pumpbody 110 a as a traveling hydraulic pump body for hydraulically drivingboth the pair hydraulic motor bodies 22 a, 22 b, and use the secondhydraulic pump body 110 b as a hydraulic source for another hydraulicactuator 30 other than the first and second hydraulic motor units 20 a,20 b.

For details, in the present embodiment, the first and second hydraulicmotor units 20 a, 20 b are fluid-connected with each other via a pair ofhydraulic motor lines 25 so as to form a closed circuit.

The first hydraulic pump body 110 a is fluid-connected to the pair ofhydraulic motor lines 25 via the pair of first operation oil lines 300a.

Specifically, the hydraulic pump unit 100G according to the presentembodiment is provided with the first and second hydraulic pump bodies110 a, 110 b, the pump case 120 for accommodating the first and secondhydraulic pump bodies 110 a, 110 b, the first and second capacityadjusting mechanisms 130 a, 130 b for respectively changing thesuction/discharge amounts of the first and second hydraulic pump bodies110 a, 110 b, and the first hydraulic servomechanism 201 a for operatingthe first capacity adjusting mechanism 130 a based on the manualoperation signal corresponding to the manual operation amount of thetravel operation mechanism 10, or both of the manual operation signaland the feedback signal.

In the present embodiment, as shown in FIG. 17, the second capacityadjusting mechanism 130 b is operated by the manual operation power viaanother control lever 50D′ without utilizing the hydraulic force.

In the hydraulic pump unit 100G, the manual operation power and themanual operation amount for operating the travel operation mechanism 10can be reduced.

Although the present embodiment is explained with taking an example ofthe case where the first hydraulic servomechanism 201 a is utilized asthe first actuator 200 a for operating the first capacity adjustingmechanism 130 a, it is of course that the first electric motor 202 acould be utilized as the first actuator 200 a.

This specification is by no means intended to restrict the presentinvention to the preferred embodiments set forth therein. Variousmodifications to the hydraulic pump unit may be made by those skilled inthe art without departing from the spirit and scope of the presentinvention as defined in the appended claims.

1. A hydraulic pump unit of variable displacement type disposed awayfrom a pair of hydraulic motor units which are capable of beingindependently arranged, the pump unit fluid-connected to the pair ofhydraulic motor units so as to change the outputs of the pair ofhydraulic motor units in both forward and reverse rotation directions,comprising: (a) a hydraulic pump body operatively rotated and driven bya driving source, (b) a pump case surrounding the hydraulic pump body,(c) a capacity adjusting mechanism for changing the capacity of thehydraulic pump body, and (d) an actuator for operating the capacityadjusting mechanism, wherein the actuator is controlled based on amanual operation signal corresponding to a manual operation amount. 2.The hydraulic pump unit according to claim 1, wherein the actuator iscontrolled based on a feedback signal corresponding to outputs of thepair of the hydraulic motor units, in addition to the manual operationsignal.
 3. The hydraulic pump unit according to claim 1, wherein thehydraulic pump body includes first and second hydraulic pump bodiesrespectively and independently fluid-connected to the pair of hydraulicmotor units; (a) the capacity adjusting mechanism includes first andsecond capacity adjusting mechanisms respectively corresponding to thefirst and second hydraulic pump bodies; and (b) the actuator includesfirst and second actuators respectively corresponding to the first andsecond capacity adjusting mechanisms.
 4. The hydraulic pump unitaccording to claim 1, wherein the pair of hydraulic motor units arefluid-connected to each other so as to form a closed circuit; and (a)the hydraulic pump body includes a single hydraulic pump body fortraveling fluid-connected to the closed circuit, and a hydraulic pumpbody fluid-connected to the other hydraulic actuator other than the pairof hydraulic motor units.
 5. The hydraulic pump unit according to claim1, wherein the actuator is a hydraulic servomechanism that includes aservo piston operatively connected to the capacity adjusting mechanismand accommodated in a reciprocating manner within a piston accommodatingchamber so as to divide the piston accommodating chamber into a regularrotation oil chamber and a reverse rotation oil chamber, asupply/discharge oil passage for supplying operating oil to anddischarging it from the servo piston, and an electromagnetic valve forswitching the supply/discharge oil passage.
 6. The hydraulic pump unitaccording to claim 1, wherein the actuator is an electronic motoroperatively connected to the capacity adjusting mechanism.
 7. Thehydraulic pump unit according to claim 6, wherein the electronic motoris connected to the capacity adjusting mechanism via a reduction gearmechanism.